You're seriously expecting Wikipedia users to set up custom css to apply their reading preferences, just so that you personally don't have to deal with a different amount of padding?
Do you realize the level of entitlement and absurdity here?
One of the two options has to be chosen for the no JS, no query param / no login default - there is no entitlement and absurdity in that expectation. Using the max-width: none or similar as the default option has the benefit of allowing the user's browser keep the ability to monotonely scale the text density along with size using zoom as the displayed area would be nearly constant. It's rather arrogant & condescending to choose for a user a width that overrides what control they have with their window's dimensions, screen size, viewing distance & vision capability.
Do you realize the level of entitlement and absurdity here?